HEAT AND SOLAR INJURIES - Medicine for Mountaineering and Other Wilderness Activities - page 415

Toavoidheatillnessinsuchcircumstances,heatproductionmustbereducedtothelow-
est possible level. Vigorous exercise must cease. In tropical areas, where temperatures and
humidity are usually high, the midday siesta is a sensible way to minimize the risk of heat
illness during the time when the threat is greatest.
In past years the most frequent causes of exertional hyperthermia in the United States
havebeendistancerunning(includingjogging)andfootballpracticeinlatesummer,which
combines vigorous physical activity, a uniform that inhibits evaporation of sweat, and a
hot, often humid environment. Recognition of the hazard associated with these activities
has led to scheduling such events in early morning when temperatures are lower. Wearing
plastic or rubberized suits while exercising to lose weight is another dangerous practice.
Such suits increase body temperature, sometimes to high levels, because they do not al-
low perspiration to evaporate. Fortunately, this practice also has been largely abandoned in
recent years, possibly more from the realization that only water—not fat—was being lost
than recognition of the danger of heat illness.
Individuals taking certain therapeutic drugs also have an increased risk of heat illness.
Anticholinergicdrugstakenforirritablebowelsyndromeandotherdisordersimpairsweat-
ing. Any of the diuretics used to treat hypertension and heart failure can lead to dehydra-
tion. Individuals taking these and other medications must be particularly cautious in hot
environments.
Water Replacement
Staggeringquantities ofwatermustbeconsumedtoreplace perspiration lossesindesert
conditions. During 1964 U.S. Army maneuvers in the deserts of southern California, for
which daytime temperatures of 100° to 110°F (38° to 43°C) were expected, participants
were required to drink eight quarts of water every day. Not a single case of heat illness oc-
curred, which was considered almost miraculous at the time. Israeli soldiers operating in
the Sinai Desert during the 1967 war with Egypt were allotted ten liters of water a day and
had no heat illnesses, which is punishable by court martial in that army. The Egyptians,
who received only three liters a day, suffered numerous fatalities due to heat illness.
Thirst alone does not provide adequate fluid intake. Individuals must make a conscious
efforttoconsumethequantitiesneeded.Duringdesertoperations,militarycommandersare
heldresponsibleforensuringtheirchargesmeetthedailyintakerequirements.Dehydration
is a major contributor to all forms of heat illness—mild and severe.
In the past, an augmented salt intake has been considered essential for preventing heat
illness. Soldiers in the California desert were required to take three to five grams of
salt—six to ten tablets—every day. That recommendation was abandoned because the diet
of residents of most industrialized nations was thought to contain enough salt for stressful
heat conditions. However, the pendulum appears to be swinging in the other direction, and
a generous salt intake seems advisable.